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In the following two AP's how many terms are identical? 2,5,8,11....to 60 terms, 3,5,7...50 terms.
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Two progressions have the number 5 common as their second term, in each progression.
Further, the first progression comes with the common difference 3, while
the second progression comes with the common difference 2.
It means that, starting from their common second term of the value 5, they will have these CANDIDATES to be common terms:
- every second term of the first progression.
- every third term of the second progression.
We also should take care that the terms belong to their common range.
The last term of the 1-st AP is 2 + 59*3 = 179.
The last term of the 2-nd AP is 3 + 49*2 = 150.
So, the common range ends at 150.
Thus the amount of common members of the 1-st AP in this common range (starting and including 5)
is the integer part of the number , i.e. 25.
And now calculating the amount of common members of the 2-snd AP in this common range (starting and including 5)
is the integer part of the number gives the same 25 (ONLY FOR CHECKING).
Answer. These two sequences have 25 numbers in common.
I think that the advise of the other tutor TO COUNT MANUALLY the common terms IS NOT THE SOLUTION and IS NOT THE METHOD OF SOLUTION.